Active Directory Migration Toolkit 3.1 does not install on Windows 2008 R2, however there is nothing wrong with installing it on Windows 2008 x64. When you start playing around with the ADMT vbscripting options you might run into the following error: “ActiveX component can’t create object: ‘ADMT.Migration"’.
The solution is easy, run the script with the x86 version of cscript.exe: “c:\windows\syswow64\cscript.exe script.vbs”
My source: TechNet forums
Why was I toying around with the vbscript instead of using the admt.exe commandline options? I wanted a way to find out which attributes are excluded by ADMT. It seems that one the first run ADMT gathers a list of attributes it will always exclude for migration. Examples are “mail” or “proxyAddresses”. The ADMT help states this could only be done through scripting. This is explained in detail in KB937537.